Acute Chest Syndrome Rate at the Emory University Georgia Comprehensive Sickle Cell Center at Grady Health System

Background: Acute chest syndrome (ACS) is one of the most feared complications of sickle cell disease. This syndrome is defined by a clinical constellation of symptoms including fever, infiltrate on lung imaging and hypoxia. ACS is a well-known complication to occur early in the hospitalization of patients for sickle cell vaso-occlusive pain crises (VOP). It is hard to differentiate from pneumonia and its rate of occurrence has not been well characterized. Management of ACS includes exchange or simple transfusion, depending on the severity of its presentation, along with critical care support and pain control. Early recognition of this clinical syndrome can lead to better management and outcomes for patients with sickle cell disease.

Methods: The Emory University Georgia Comprehensive Sickle Cell Center at Grady Health System has 1073 sickle cell patients and provides a 24/7 acute care unit (ACU) for the evaluation of patients presenting with pain crises. We conducted a retrospective review of all the ACS cases reported at the Center for the last 5 years.

Results: The number of sickle cell patient-visits in the ACC was 4409. 30 cases of ACS were confirmed on retrospective review. The rate of ACS was 6.8 per 1000 patient visits. The median age was 39, and the patients' phenotypes 89% SS and 11% SC. Of the patients evaluated, 18% were smokers, 43% were taking hydroxyurea and 89% were taking folic acid. Seventy five percent of the patients were successfully managed with supportive care only, while the remaining 25% required red cell exchanges. On admission, the median white cell count (WBC), platelet count, LDH and reticulocyte count were increased above their upper limits of normal. Eighteen percent of the patients had a d-dimer checked and the median was well above the range of normal (6097). Table 1 shows the patient characteristics and data.

Discussion: The rate of ACS over the last 5 years at our sickle cell center is well below historic reports of ACS. We believe that several factors explain our observation. Because our 24/7 ACU is staffed with providers who know their patients' histories and treatment plans and are experienced in the management of VOP, we postulate that our comprehensive management approach involving the rapid and appropriate initiation of intravenous fluids, the administration of pain medications along with antibiotics, and the use of anti-inflammatory medications contribute to the truncation of the sickle cell-related inflammatory state and the prevention of serious complications such as ACS. The fact that inflammatory markers (WBC, Platelet count, LDH) were initially elevated is to be expected in the setting of VOP. What is remarkable is the high percentage of good patient outcomes associated with our comprehensive management approach. This retrospective report should be validated in a prospective study that compares the results of the management of all acute care VOP visits delivered in a 24/7 ACU with the management of acute care VOP delivered in a general emergency room. Such a study should include the collection of laboratory and clinical data that is typically abnormal in patients with VOP. If a significantly decreased rate of ACS rate is observed when 24/7 ACU care is provided, then the institution of 24/7 acute care units would be warranted on a national level to improve the survival of patients with sickle cell disease.

Characteristics of patients studied
Age median (range)	39 (19-58)
Gender	Females 14/ males 14
Genotype n (%)	SC 3 (11%)/ SS 25 (89%)
Smoking (%)	18 %
Hydrea use (%)	43%
Folic acid use (%)	89%
Management n (%)	Exchanged 7 (25%)/ supportive 21 (75%)
Hemoglobin median (range)	10.4 (4.9-11.1)
White count median (range)	18.6 (6.1-47)
Platelet median (range)	492 (79-646)
Reticuolcyte count median (range)	300.6 (151-597)
LDH median (range)	677 (238-2287)
D-dimer % patients/ median (range)	18%/ 6097 (609-33370)
Ferritin % patients/ median (range)	11%/ 2844 (335.2-6060)
Total/direct bilirubin median (range)	3.7/1.3 (1-19/0.2-4.9)
Creatinine median (range)	1.3 (0.5-3.5)
AST/ALT median (range)	59/49 (21-110/12-118)